Engine Air Filter and Sealing System

ABSTRACT

An air induction system for an engine to remove contaminants from intake air prior to delivery to the engine. The system includes an assembly for filtering air which is mounted in advance of the engine, and a duct for delivering air from the assembly to the engine. A sealing system is provided which prevents entry of unfiltered air while simultaneously permitting movement of the engine relative to adjacent parts of the airframe as engine power setting varies. The seal is protected from high pressures in the duct which can occur in operation of the engine.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/823,934, filed Apr. 14, 2004, the entirety of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to air intakes for engines, and inparticular to a system for mounting and sealing a barrier filter whichprotects an aircraft engine.

An engine for aircraft propulsion requires intake air that is free fromcontaminants to provide for efficient combustion and avoid internaldamage. The compressor and turbine are designed with small tolerancesbetween moving parts which maximize efficiency, but which also increasevulnerability to damage from small foreign particles. Contamination ofintake air, even in a small amount, causes premature wear on enginecomponents, increases maintenance costs, and degrades operationalreliability. Unfortunately, aircraft are exposed to contaminants whenoperating at low altitudes where air is frequently contaminated withmaterial from the ground, such as sand and dust. That problem isaggravated for helicopters due to rotor downwash and prolongedlow-altitude operation.

Systems which remove foreign particles from intake flow have beendeveloped to protect the engine from damage. In many instances, such asystem includes an intake housing having a contaminant separator, suchas a filter, positioned in advance of the engine inlet, with airtightseals at interfaces to prevent entry of unfiltered air. Effectivesealing is difficult to implement and maintain because the engine movesrelative to adjacent parts of the airframe as its power setting varies.For example, the front end of the engine may deflect about one inch asits power increases, with the movement being in a direction having allthree directional components with respect to the airframe (e.g.,forward, inboard, and down). Unfortunately, seals have been stiff orinsufficiently flexible to move in this way while maintaining airtightintegrity. They have typically been made of stiff materials because theyare located where they must withstand pressure in the inlet. Further,seals are prone to fail when exposed to strong differential pressures ifthe engine should experience a surge instability that suddenly increasesinlet pressure. Aggravating the difficulty is that the filter must beaccessible for maintenance actions, cannot obstruct accessibility to theengine or airframe, and should not introduce loads to the inlet.

SUMMARY OF THE INVENTION

Among the several objects and features of the present invention that maybe noted the provision of an engine intake air filtration system whicheffectively removes contaminants; the provision of such a system whichis usable in existing aircraft without substantial modifications; theprovision of such a system which readily permits movement of the enginerelative to the surrounding airframe; the provision of such a systemwhich is not adversely affected by unusually high pressures; theprovision of such a system which minimizes loss and non-uniformity ofpressure to the intake flow; the provision of such a system which isreadily accessible for maintenance; the provision of such a system whichis lightweight; and the provision of such a system which is economical.

In general, an air induction system of the present invention is for anengine to receive intake air, remove contaminants from the intake air,and provide the intake air for delivery to the engine. The systemcomprises a housing having a hollow interior with at least one entrywayfor receiving intake air into the housing, a contaminant separator forremoving contaminants from the air, and an exit for discharge of airfrom the housing. A duct is positioned adjacent the exit of the housingto receive intake air therefrom for delivering the air to the engine.The duct has an inside defining an internal flow path for intake air andan outside. A seal is positioned between the housing and the duct forpreventing passage of air therethrough. The seal is disposed between theoutside of the duct and the housing such that the seal is not exposed toair flowing in the internal flow path of the duct.

In another aspect, an air induction system of the invention is for anaircraft engine to remove contaminants from intake air and deliver theair to the engine. The system comprises a contaminant removal assemblyfor receiving intake air and removing contaminants from the air. Theassembly has at least one entryway for receiving intake air and an exitfor discharge of the air from the assembly. A duct is configured toreceive intake air from the assembly for delivery to the engine. Aflexible and resilient seal is positioned between the assembly and theduct for preventing entry of contaminated air. The seal permits relativemovement between the duct and the assembly in any direction whilemaintaining a seal between the duct and the assembly.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective of a helicopter having an airinduction system according to the present invention;

FIG. 2 is an enlarged portion of FIG. 1;

FIG. 3 is an elevation of a nacelle, duct, and inlet of the airinduction system;

FIGS. 4 and 5 are front and rear perspectives of a filter panel for usein the nacelle;

FIG. 6 is a perspective of the nacelle swung to an open position;

FIG. 7 is a top plan of the nacelle swung to the open position;

FIG. 8A is a fragmentary bottom plan of the air induction system at thejunction of the duct and the nacelle with the nacelle at the closedposition;

FIG. 8B is a view similar to FIG. 8A with the nacelle at the openposition;

FIGS. 9A and 9B are perspectives of the duct with a seal installedaround an outer circumference;

FIGS. 10A and 10B are front and rear perspectives of the seal;

FIG. 11 is a perspective of a frame for supporting the nacelle; and

FIG. 12 is a section taken along line 12-12 of FIG. 3.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIG. 1, an airinduction system of the present invention is designated generally by 20.The system 20 includes filters 22 for protecting an engine (not shown)from ingestion of contaminant particles. The system is primarilyintended for use with a gas turbine engine which is installed in anaircraft 24, such as a UH-60 Blackhawk helicopter. However, it isunderstood that the system 20 can be used with other types ofair-breathing engines, for installation at a facility or factory, or foruse on a portable cart, without departing from the scope of thisinvention.

The system 20 includes a nacelle 26 and a transition duct 28 which arepositioned forward of an inlet 30 and which provide intake air to theinlet for delivery to the engine. There are two such systems 20 aboardthe helicopter 24 for two corresponding inlets 30. The nacelle 26comprises a housing having four outer sides and a hollow interior, eachside having an opening which mounts a filter panel 32 having a filter 22for receiving intake air into the housing. The shapes and sizes of thenacelle 26 and filters 22 may be selected to fit the particular aircraftwith a configuration producing a favorably mechanical and aerodynamicintegration, and alternate shapes or configurations do not depart fromthe scope of this invention. Moreover, the number and orientations ofthe filter panels may vary.

The nacelle 26 has a forward-facing door 34 which is movable between aclosed position and an open position. A conventional actuator (notshown) for moving the door 34 is located in the interior of the nacelle.During normal operation, the door 34 remains closed so that all intakeair must enter the nacelle 26 in a generally radial direction throughone of the filters 22 in a corresponding filter panel 32. Duringoperation when the filters 22 have become laden with dirt or becomeclogged, the door 34 is opened, defining a alternate, bypass passagewayso that the engine has sufficient air to continue operation. The door 34is swept at an acute angle with respect to the forward direction toreduce aerodynamic drag and reduce impact force from bird strikes.

The nacelle 26 is supported directly by the airframe of the aircraft 24so that forces on the nacelle are not transmitted to the engine. Arectangularly-shaped frame 36 (FIGS. 2, 6, and 11) at a rearward side ofthe nacelle is fixedly attached to the airframe structure by bolts atfastening formations 38 and by upper and lower struts 40. The frame 36provides a mount for the nacelle 26, and it bears the weight andaerodynamic forces of the nacelle. Other configurations for supportingthe nacelle do not depart from the scope of this invention. The frame 36may have a one-piece construction (i.e., a plate) or may be an assemblyof two or more components. An opening 42 in the frame 36 defines anacelle exit for discharge of air from the nacelle 26 toward the engine.A flange 44 (FIG. 11) extending around the opening projects axially(toward the engine) from the frame 36.

The nacelle 26 is attached to the frame 36 by hinges 46 for swingingmotion between a closed position (FIGS. 1-3) for engine operation and anopen position (FIGS. 6 and 7) for maintenance, cleaning, or inspection.At the closed position, the frame 36 defines an end wall of the hollowinterior of the nacelle 26. A bulb seal 48 (FIG. 6) extends around therear of the nacelle for engaging the frame 36 and sealing the interfacebetween the nacelle and frame so that unfiltered air cannot enter thenacelle. Two removable pins (not shown) are provided to secure the frontof the nacelle 26 to the airframe when the nacelle is at the closedposition. A person may unfasten the pins and swing the nacelle 26 fromthe closed position to the open position. At the open position,maintenance personnel have ready access to the filter panels 32 forcleaning or replacement, and can see directly through the duct 28 to theengine face for visual inspection. Moreover, in the open position, thenacelle is swung away from the helicopter fuselage providing unhinderedaccess for a maintenance person to reach the upper side of thehelicopter 24.

A rod 50 (FIG. 6) secures the nacelle 26 at the open position so that itwill not inadvertently move, such as when struck by a gust of wind orwhen the helicopter 24 rests on an incline. As shown in FIGS. 8A and 8B,a slot (indicated generally at 52) extends along a lower surface of theframe 36. The slot 52 has a linear portion 54 and receives a first end56 of the rod 50 for sliding motion therein to guide movement of the rodas the nacelle swings open. The slot has an end 58 which extends at anangle from the linear portion 54 and defines a locking position for therod 50. A second end 60 of the rod 50 is secured to a lower surface ofthe nacelle 26. As the nacelle swings from the closed position (FIG. 8A)to the open position (FIG. 8B), the first end 56 of the rod slides alongthe slot 52. Upon reaching the end of the linear portion 54 of the slot(where the nacelle is at the full open position), the first end 56 ofthe rod automatically snap-locks into the angled end 58 of the slot. Atorsional spring 62 (FIG. 6) at the second end 60 urges the rod 50 tothe locking position, thereby automatically locking the rod, and holdsit at that position until manually released. Other configurations forguiding movement of the nacelle and securing it do not depart from thescope of this invention.

Each filter panel 32 (FIGS. 4 and 5) includes a pleated barrier filterelement 22 mounted in a retention frame 64 which securely retains thefilter element in place, yet allows for its easy replacement. Theretention frame 64 engages edges of a corresponding opening in thenacelle 26, forming a seal such that all air must pass through thefilter element 22 to reach the interior of the nacelle. A rim 66 of eachfilter panel 32 has holes 68 for receiving fasteners (not shown) toconnect to the nacelle 26. An exemplary material for the retention frame64 is aluminum, although other materials may be used. The filter element22 is held in place in the retention frame 64 by a suitable adhesion orphysical connection, such as by a polymeric potting material such aspolysulphite or polyurethane, or by an epoxy. The potting materialfunctions as a sealant to seal the perimeter (i.e., side edges) of thefilter element 22, structurally adhering it to the retention frame 64and preventing unfiltered air from passing between the retention frameand the filter element. Each filter is constructed such that if itshould become plugged with contaminants to a degree where adequateairflow can not be provided to the engine, maintenance personnel canreadily clean the barrier filter media by backflushing with a spray ofwater.

Pleating of the barrier filter element 22 effectively increases thesurface area and rigidity of the filter element. The filter element iseffective at separating contaminants from the air and provides a lowpressure drop characteristic across the filter. The filter element 22 isconstructed of filter media capable of achieving high particle removalefficiencies. The filter media is made of a lightweight material thatwill also be resistant to damage by water and other liquids it mayencounter in operation. Preferred filter media includes woven cotton orpolyester or a felt. When cotton is employed as the filter media, thefilter media is preferably a cotton grid fabric comprised of a pluralityof overlapping layers of woven cotton material. Preferably, the numberof layers is in the range of from 3 to 6. The filter media may bestrengthened by a stainless steel screen (not shown) which lines thefilter media. To improve the filter efficiency for finer particles, thefilter media may be impregnated with oil, which not only improvesparticle removal, but also helps resist moisture absorption by thefilter media rendering it waterproof. A comb 70 (FIG. 5) extends acrossa center of the backside of each filter panel 32 to strengthen andmaintain separation of the pleats. A lift ring 71 (FIG. 4 ) is used toassist in installation, removal and transporting of filter panels.

It is understood that contaminant separators of various otherconfigurations, such as non-pleated filters, filters formed with adifferent construction, and non-filtering inertial particle separators,do not depart from the scope of this invention.

The duct 28 (FIGS. 6, 9A, and 9B) receives intake air from the interiorof the nacelle 26 and delivers it to the engine inlet 30. A front of theduct 28 is positioned generally at the exit of the nacelle 26, and it issized and shaped to fit through the opening 42 of the frame 36. There isno engagement of the frame 36 by the duct 28. Rather, the duct 28 issuspended within the opening 42. A bell-mouth shaped end 72 draws asmooth stream of intake air with minimal loss of pressure and minimalnon-uniformity to flow properties across the stream. The contours of theduct 28 change the cross-section of the stream from a generally circularshape at its front end 72 to a bent oval, or kidney shape (FIG. 9B) atits back end 74 corresponding with a shape of the inlet 30. The duct 28has a length, contour, and shape which are highly dependent on theparticular aircraft and inlet upon which it is installed. Theseparameters may differ from the illustrated embodiment, or there may beno duct distinct from that of the inlet, without departing from thescope of this invention. When installed, the outer surface of the duct28 is spaced from the opening of the frame 36 to permit relativemovements without contact therebetween. Because the duct 28 ispreferably formed of a rigid and lightweight material (e.g., a brittlecomposite such as a carbon fiber reinforced epoxy resin), any contactwith the frame 36 could cause damage. Typically, a spacing between theouter surface of the duct and edge of opening 42 is about two inches,which provides adequate separation.

The duct 28 is attached to and supported by the inlet 30 (which in turnis supported by the engine) such that the duct and inlet move conjointlywith the engine as power varies and the engine shifts position in theairframe. As shown in FIG. 9B, the back end 74 of the duct comprises aninner portion 76 for being received inside the inlet 30 and an outerportion 78 comprising a skirt which engages the outer surface of theinlet. The skirt 78 forms an interface having a smooth contour andgenerally airtight connection. Because the duct 28 moves with theengine, seals between the inlet and duct at the back end 74 of the ducthave no requirement to compensate for relative motions and may thereforebe simple and lightweight. For example, the skirt 78 may be formed of a3/16-inch thick soft foam rubber. A similar internal soft blade seal(not shown) may be positioned at the junction of the inner portion 76 ofthe duct and the inlet 30. Several latches 80 are provided on the outerside of the duct 28 for connection to cables 82 (FIG. 3) on the exteriorof the inlet 30. The cables 82 extend between anchors 84 which arefastened to the inlet 30. Preferably, the anchors 84 use pre-existingfastener holes such that the helicopter 24 does not require modificationor driling of holes when fitted with the system 20 of the presentinvention.

A flexible and resilient seal 86 is positioned between the nacelle 26and the duct 28 for preventing entry of unfiltered air through theopening 42 of the frame 36 between the outer surface of the duct and theedge of the opening. The seal 86 extends around an outer circumferenceof the duct 28, and is preferably a single piece or band of flexiblematerial with its ends bonded or spliced together forming a ring shape.

Significantly, the seal 86 is positioned outside the duct 28 such thatthe seal is not exposed to air flowing in the flow path inside the duct.Therefore, the seal 86 is unaffected by pressures in the duct 28,including particularly a sudden rise in pressure due to a surgeinstability in the engine. Because the seal 86 is not exposed to highpressures, it can be more lightweight and flexible. The seal permitsrelative movement between the duct 28 and the nacelle 26 without contacttherebetween, thereby precluding the possibility of damage. Moreover,the airtight seal between the duct and nacelle is maintained. The seal86 is formed of a suitably elastic material which permits movement ofthe duct relative to the nacelle in a direction having any or all threedirectional components with respect to the airframe (i.e., longitudinal,lateral, and elevational) without binding or failing. The seal 86 may bestretched a significant distance (e.g., twice its unloaded dimension(s))without damage, and will return to its original position when unloaded.Preferably, the material is lightweight and inexpensive. An exemplarymaterial is silicon rubber.

Because the seal 86 does not form a portion of the surface exposed tothe airstream, an additional length may be included to create a slack or“baggy” portion which further facilitates relative movement. In oneembodiment, additional length is provided for slack of about twice thelength required (e.g., unloaded length of four inches instead of two).

Referring to FIG. 12, the seal 86 is clamped on opposite edges. A firstedge is attached to the frame 36 by fitting it around the flange 44extending around the frame opening 42. A conventional band clamp 88(FIG. 10A) extends around the flange 44 and tightens against the seal 86to hold it firmly against the flange 44. The seal 86 is attached to theduct 28 by clamping it between a ring 90 and retainer plate 92, as shownin FIG. 12. The ring 90 is a rigid protrusion having an L-shaped bodywhich is fixed to the outer surface of the duct 28 by an epoxy or othersuitable method. Preferably, the ring 90 is formed of a lightweightcomposite material, such as a carbon fiber reinforced epoxy resin.Several thin retainer plates 92 (e.g., two) are spaced around thecircumference of the duct 28 and are attached to the ring 90 by suitablefasteners 94, such as a bolt or rivet. Each retainer plate 92 holds theseal 86 in sandwiched position against the ring 90. Other systems forholding the seal in position do not depart from the scope of thisinvention.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

1. An air induction system for an engine to receive intake air, removecontaminants from the intake air, and provide the intake air fordelivery to the engine, the system comprising: a housing having a hollowinterior with at least one entryway for receiving intake air into thehousing, a contaminant separator for removing contaminants from the air,and an exit for discharge of air from the housing; a duct positionedadjacent the exit of the housing to receive intake air therefrom fordelivering the air to said engine, the duct having an inside defining aninternal flow path for intake air and an outside; and a seal positionedbetween the housing and the duct for preventing passage of airtherethrough; wherein the seal is disposed between the outside of theduct and the housing such that the seal is not exposed to air flowing inthe internal flow path of the duct.
 2. An air induction system as setforth in claim 1 wherein the seal is flexible and resilient.
 3. An airinduction system as set forth in claim 2 wherein the seal comprises anannular band clamped along opposite edges to the housing and duct.
 4. Anair induction system as set forth in claim 3 wherein the seal is made ofsilicon rubber.
 5. An air induction system as set forth in claim 1wherein the housing further comprises a nacelle and a frame at a backend of the nacelle, the frame having an opening therein comprising saidexit, and wherein a front of the duct is received through the opening.6. An air induction system as set forth in claim 5 wherein the sealextends between the outside of the duct and the opening in the frame. 7.An air induction system as set forth in claim 6 wherein the frame has aflange extending around the opening, the seal being clamped against theflange.
 8. An air induction system as set forth in claim 6 wherein theduct has a rigid protrusion on its outside, the seal being clampedagainst the protrusion.
 9. An air induction system as set forth in claim8 wherein the protrusion comprises an L-shaped body extending in a ringaround the outside of the duct.
 10. An air induction system as set forthin claim 1 wherein said entryway comprises an opening formed in thehousing, the contaminant separator being mounted across the entryway.11. An air induction system as set forth in claim 10 wherein thecontaminant separator comprises a barrier filter having a porous media.12. An air induction system as set forth in claim 1 wherein the housingfurther comprises a nacelle and a frame on a back end of the nacelle,the nacelle being hinged to the frame for swinging movement between aclosed position for engine operation and an open position formaintenance.
 13. An air induction system as set forth in claim 12further comprising a rod which secures the nacelle at the open positionso that it will not inadvertently move.
 14. An air induction system asset forth in claim 13 wherein the rod has a first end secured to theframe and a second end secured to the nacelle, the first end beingslidably movable in a slot attached to the frame.
 15. An air inductionsystem as set forth in claim 14 wherein the rod and slot are shaped andarranged to assume a locking position when the nacelle swings to theopen position.
 16. An air induction system as set forth in claim 15further comprising a spring at the second end urging the rod to lock thenacelle at the open position.
 17. An air induction system for anaircraft engine to remove contaminants from intake air and deliver theair to the engine, the system comprising: a contaminant removal assemblyfor receiving intake air and removing contaminants from the air, theassembly having at least one entryway for receiving intake air and anexit for discharge of the air from the assembly; a duct configured toreceive intake air from the assembly for delivery to said engine; and aflexible and resilient seal positioned between said assembly and theduct for preventing entry of contaminated air; wherein the seal permitsrelative movement between the duct and the assembly in any directionwhile maintaining a seal between the duct and the assembly.
 18. An airinduction system as set forth in claim 17 wherein the seal comprises anannular band clamped along opposite edges to the contaminant removalassembly and the duct.
 19. An air induction system as set forth in claim18 wherein the seal is made of silicon rubber.
 20. An air inductionsystem as set forth in claim 17 wherein the contaminant removal assemblyfurther comprises a nacelle and a frame at a back end of the nacelle,the frame having an opening therein comprising said exit, and wherein afront of the duct is received through the opening.
 21. An air inductionsystem as set forth in claim 20 wherein the nacelle is hinged to theframe for swinging movement between a closed position for engineoperation and an open position for maintenance.
 22. An air inductionsystem as set forth in claim 21 further comprising a rod which securesthe nacelle at the open position so that it will not inadvertently move.